In oxygen concentrators, oxygen is obtained in accordance with a pressure swing adsorption method in which oxygen in raw air is caused to pass through, for instance, a zeolite or the like, as an adsorbent, that selectively adsorbs nitrogen.
An air intake opening for intake of raw air is provided in a main body cover of an oxygen concentrator of this type. Raw air taken in via this air intake opening is compressed by a compressor, as a compression unit, to generate compressed air thereby. The compressed air is fed to an adsorbent-packed adsorption barrel, where nitrogen is adsorbed onto the adsorbent, to yield oxygen as a result. The generated oxygen is stored in a tank and is brought to a state that enables supply of a predetermined flow rate of oxygen from the tank, via a reducing valve or a flow rate setting unit. Thereby, a patient can inhale the oxygen using an implement such as a nasal cannula.
For instance, patients having impaired lung function and being under home oxygen therapy can breathe oxygen safely even when in bed, and can sleep hence soundly, if such an oxygen concentrator is installed at a site where AC power source (commercial AC power source) can be used.
Preferably, the oxygen concentrator makes very little noise, in particular, when used in bed by patients under home oxygen therapy. Preferably, the noise of the oxygen concentrator does not exceed, for instance, the noise level of indoor air conditioning.
Oxygen concentrators used for long-term oxygen therapy, which is effective as a therapy for patients having a respiratory disease such as chronic bronchitis, are ordinarily not transportable, and are not configured to be carried to such sites as the patient may move to. When the patient is forced to go out, he/she must inhale concentrated oxygen out of an oxygen cylinder, being a container of a predetermined capacity filled with oxygen and placed on a cart that is pushed by the patient. Such oxygen and cylinders must be filled at dedicated facilities. Thus, transportable and/or mobile oxygen concentrators have been proposed wherein the transportable or mobile oxygen concentrator is provided with a battery-drivable compressor that comprises a compression unit for generating compressed air by taking raw air in, and with a pressure reduction unit for generating reduced-pressure air (Patent document 1).    Patent document 1: Japanese Patent Application Laid-open 2002-45424